From: James Edward Gray II <james@...>
Date: 2006-08-10T01:43:59+09:00
Subject: Re: Code structure and using "require"

On Aug 9, 2006, at 11:26 AM, Jean Nibee wrote:

> Hi
>
> I'm coming from a java world and I'm trying to understand the  
> structure
> of a Ruby project and how 'require's are resolved.

Welcome to Ruby.

I'll see if I can explain a little.  A require searches Ruby's load  
path with the required path being relative from each location listed  
in there.  You can find Ruby's load path on your box with something  
like:

   $ ruby -r pp -e 'pp $LOAD_PATH'
   ["/usr/local/lib/ruby/site_ruby/1.8",
    "/usr/local/lib/ruby/site_ruby/1.8/i686-darwin8.5.2",
    "/usr/local/lib/ruby/site_ruby",
    "/usr/local/lib/ruby/1.8",
    "/usr/local/lib/ruby/1.8/i686-darwin8.5.2",
    "."]

Notice that the last entry is the working directory.  This means that  
you can:

   require "lib/whatever"

to load whatever.rb in the lib directory inside the current working  
directory.

You can also influence the load path at runtime:

   $ ruby -I lib -r pp -e 'pp $LOAD_PATH'
   ["lib",
    "/usr/local/lib/ruby/site_ruby/1.8",
    "/usr/local/lib/ruby/site_ruby/1.8/i686-darwin8.5.2",
    "/usr/local/lib/ruby/site_ruby",
    "/usr/local/lib/ruby/1.8",
    "/usr/local/lib/ruby/1.8/i686-darwin8.5.2",
    "."]

This is commonly used in testing.  Assuming we have a standard Ruby  
project structure of something like:

   project/
     bin/
     doc/
     example/
     lib/
     test/
     util/

tests are generally run from the project directory with a command like:

   $ ruby -I lib:test test/ts_all.rb

Hope that helps.

James Edward Gray II